The invention relates to a device for detecting the position of a selector lever, in which the selector lever is connected to a device that emits a signal to an evaluation device in a desired position of the selector lever.
In many areas of application, there are selector levers that can be moved backward and forward in one direction, latcahed in or can be fixed in predetermined positions and control the operation of a connected unit as the operating elements. It is desirable to detect the position of the selector lever in order to be able to control more effectively a system in which the unit controlled by the selector lever is incorporated. In a motor vehicle, information as to which transmission stage has been chosen is necessary for automatic speed control, for example.
According to U.S. Pat. No. 4,523,373, an actuating lever with a potentiometer is known, it being possible at all times to pick off from the potentiometer a voltage corresponding to the position of the selector lever. The potentiometer is installed in a housing in such a way that the same signal voltage is always emitted in a preselected position of the lever. Such contact-controlled position detection systems are subject to wear due to abrasion and dirt accumulation, resulting in variation of the signal voltage corresponding to a particular position of the selector lever over the service life of the potentiometer. There is no longer an unambiguous association between the voltage and the position of the selector layer.
The object on which the invention is based is to provide a device for detecting the position of a selector lever that operates reliably over its entire service life and can be produced at reasonable cost.
According to the invention, the selector lever is connected to a diaphragm arranged in the beam path between an optical transmitter and an optical receiver, the diaphragm, which follows the movements of the selector lever, being optically transparent in the desired position of the selector lever, as a result of which the optical receiver receives the signal from the optical transmitter and transmits it to the evaluation device.
The advantage of the invention resides in the fact that position detection is contactless. The switching device of the selector lever thus operates completely without wear. It is simple in construction and sufficiently robust for use in a motor vehicle.
Unambiguous detection of the position of the selector lever is ensured by the fact that there is an optical receiver for each position of the selector lever to be determined and that an opening in the diaphragm is moved over the optical receivers as the selector lever is moved.
For an embodiment that is particularly robust for use in motor vehicles, the optical receivers are arranged in a fixed manner on a carrier element in accordance with the sequence of motion of the selector lever.
A particularly compact and small switching device is achieved by arranging the evaluation device connected to the optical receivers on the same carrier element.
In a refinement, at least one optical transmitter is arranged on the carrier element, the optical signal of which can be deviated onto the diaphragm by means of a light guide. Such a device can be used in a flexible manner at any desired point of installation.
To enable the movement of the selector lever in different directions of motion to be detected unambiguously, one diaphragm is provided for each direction of motion of the selector lever. Here, the diaphragms can be moved in mechanical isolation from one another. By virtue of this arrangement, all positions, both in the horizontal and/or vertical direction of motion of the selector lever, are reliably detected.
The second diaphragm, which follows the selector lever in an approximately vertical direction, advantageously has two optically transparent openings, the approximately vertical movement of the selector lever being converted into a circular-arc-like movement of the diaphragm.
To ensure uniform distribution of the optical signal over the diaphragms, the light guide is provided to cover an extended area.